The present invention is directed to a communication net for use in the fire alarm and security field and a specific communication protocol wherein various devices, particularly fire alarm and security devices, are monitored and/or controlled. All communication takes place by logic "1"s and "0"s. Pulse code modulation, frequency shift key transmission and the like is avoided. Devices are monitored and controlled by peripherals connected to a pair of communication lines emanating from a central panel cpu. Each peripheral is assigned a unique address by which the peripheral is polled by the central panel. Each peripheral may be polled so as to report back as to the status of one or more devices being monitored by the peripheral, or to control one or more output devices as instructed by the central panel.